At present, there are more and more position services based upon the location of a mobile terminal, with the development of mobile communication technologies and a growing demand for the services. The location-based services relate to traffic, logistics, securities, emergences, daily life and other various fields and can provide navigation, logistical management, traffic information, schedules and other numerous services and thus have been widely applied.
In a system for positioning a mobile terminal, position calculation is typically performed for the mobile terminal based on signal strength, a carrier phase, a measured angle at which a signal arrives and time of arrival measurement, and a combination thereof. At present the mobile terminal can be positioned in two approaches, that is, it can be positioned in the control plane or in the user plane. The mobile terminal is positioned in the control plane by use of a signalling link between a Radio Network Controller (RNC) and a Core Network (CN), particularly as follows: the CN transmits a position request to the RNC to trigger a position process, and the RNC sends a position result to the CN after the mobile terminal is positioned, wherein the CN, the RNC and a Node B are involved in the position process; and the mobile terminal is positioned, in such a way that the mobile communication device communicates with a position server, over an Internet Protocol (IP) link, without modifying the existing infrastructure of a mobile communication network, that is, the position process relates to an access to a Packet Switched (PS) domain service for the RNC and the Node B, and all of position control signalling and measurement data is exchanged directly between a position control center of a core network and a User Equipment (UE).
In the prior art there are generally the following position schemes based on, e.g., a Cell Identity (ID), an Observed Time Difference of Arrival (OTDOA), an Assisted Global Position System (A-GPS), etc.
The several existing position schemes will be described below.
1. Position Scheme based on a Cell ID:
In the position scheme based on a cell ID (i.e., the coverage area of a cell), the ID of a cell where the mobile terminal resides is determined, and further the mobile terminal is positioned by the longitude and the latitude of the cell, that is, the precision of position is generally decided by the radius of the cell. This scheme is easy to implement with a short response time by occupying a small number of resources at the cost of a low precision of position.
2. Position Scheme based on OTDOA:
In the position scheme based on OTDOA, the location of the mobile terminal is determined by detecting the time difference of arrival of signals from two Node Bs, and the measurement quantity is System Frame Numbers (SFNs)−SFN Observed Time Difference, which is measured by the UE. The position scheme based on OTDOA involves more than three Node B's measuring the position parameters concurrently for a higher precision of position.
3. A-GPS Position Scheme:
In the A-GPS position scheme, the mobile terminal is provided with assistance GPS information over the network, the mobile terminal captures a satellite and receives measurement information, and then the mobile terminal calculates the location thereof or transmits the measurement information to the network, and the network calculates the location of the mobile terminal. The mobile terminal is specially required in the A-GPS position scheme that the mobile terminal has to be provided with a GPS module therein. The A-GPS position scheme has a high precision of position outdoors but has a low precision of position and even does not work indoors or in a shielded environment.
Moreover there is also such a TA plus AOA position scheme specific to a Time Division Synchronized Code Division Multiple Access (TD-SCDMA) system, that location calculation is performed for the mobile terminal by using an Angle of Arrival (AOA), a RX Timing Deviation (RxTD), a Timing Advance (Tadv) and other measurement parameters, wherein Tadv is measured by the UE, and the AOA and the RxTD are measured by the Node B.
A Stand-alone Serving Mobile Location Center (SMLC) (SAS) network element has been introduced to the 3th Generation Partnership (3GPP) Standard Release 5 (R5), to function as a Position Calculation Application Part (PCAP) in the network architecture as illustrated in FIG. 1. A logical interface between the SAS and the RNC is an Iupc interface, generally configured to transmit messages related to position information of the UE between the RNC and the SAS.
In the 3GPP Standard R5, the PCAP function can only be performed in the A-GPS position scheme. Since the R6, the PCAP function can also be performed in the cell ID-based position scheme, the OTDOA-based position scheme, the TA plus AOA position scheme and the other various position schemes.
Referring to FIG. 2A, a flow of performing the PCAP function in the OTDOA-based position scheme includes the following operations:
Operation a1: The CN transmits a position request message to the RNC;
Operation b1: The RNC transmits a measurement control message to the UE, to request the UE for an OTDOA-related measurement, and the OTDOA-related measurement quantity is an SFN-SFN Observed Time Difference;
Operation c1: The UE sends a measurement report carrying an OTDOA-related measurement result to the RNC;
Operation d1: The RNC transmits a PCAP calculation request message carrying the OTDOA-related measurement information to the SAS via the Iupc interface;
Operation e1: The SAS performs position calculation according to the carried related measurement information, derives geographical location information of the UE, and sends a PCAP calculation response message carrying a result of calculating the location of the UE to the RNC via the Iupc interface; and
Operation f1: The RNC sends a position result to the CN.
Referring to FIG. 2B, a flow of performing the PCAP function in the TA plus AOA position scheme includes the following operations:
Operation a2: The CN transmits a position request message to the RNC;
Operation b2: The RNC transmits a measurement control message to the UE, to request the UE for Tadv measurement;
Operation c2: The UE sends a measurement report carrying a Tadv measurement result to the RNC;
Operation d2: The RNC transmits a dedicated measurement request message to the Node B to request the Node B for RxTD measurement and AOA measurement;
Operation e2: The Node B sends a dedicated measurement report carrying RxTD measurement and AOA measurement results to the RNC;
Operation f2: The RNC transmits a PCAP calculation request message carrying Tadv, RxTD and AOA related measurement information to the SAS via the Iupc interface;
Operation g2: The SAS performs position calculation according to the carried related measurement information, derives geographical location information of the UE, and sends a PCAP calculation response message carrying a result of calculating the location of the UE to the RNC via the Iupc interface; and
Operation h2: The RNC sends a position result to the CN.
In a practical application, the related measurement information in the dedicated measurement report message sent by the Node B is as depicted in Table 1:
TABLE 1Information element/Optional orgroup namerequiredRangeNoteSelected dedicatedRequiredmeasurement type>Signal to interferenceratio>Transmit code power>Additional dedicatedmeasurement type>>Rx timing deviationRequiredApplicable to1.28 Mcps TDD.>>>Rx timing deviation>>Angle of arrivalApplicable to1.28 Mcps TDD.>>>Angle of arrivalRequired>>> Required precisionRequiredof angle of arrival>>Best cell portionsApplicable to1.28 Mcps TDD.>>>Best cell portionsRequired
Information contents of the best cell portions are as depicted in Table 2:
TABLE 2Information element/Optional orgroup namerequiredRangeNoteBest cell portion1 . . . <The largest numberof best cell portions>>Cell portion identifierRequired>Received signal codeRequiredpower
In a practical application, contents of the PCAP calculation request message are as depicted in Table 3:
TABLE 3Information element/Optional orgroup namerequiredRangeNoteMessage typeTransaction identifierRequiredInitial UE location estimationOptionalGPS measurement result0 . . . 3>GPS measurement resultRequiredMeasurement result set based0 . . . 16on cell identifier>Measurement result informationRequiredlist based on cell identifierOTDOA measurement group0 . . . 1>OTDOA reference cell information>OTDOA adjacent cell list information1 . . . 32>>OTDOA adjacent cell informationRequired>OTDOA measurement result set1 . . . 16>>OTDOA measurement resultinformation list
In a practical application, contents of the measurement result information list based on cell identifier are as depicted in Table 4:
TABLE 4Information element/Optional orgroup namerequiredRangeNoteMeasurement result1 . . . 32information based on cellidentifier>Measured cell identifierRequired>Node B antennaRequiredgeographical locationinformation>Rx timing deviation0 . . . 1Applicable toinformation1.28 Mcps TDD.>>Rx timing deviationRequired>>Timing advanceRequired>>Extended timing advanceOptional>Path lossOptional>Angle of arrival0 . . . 1Applicable to1.28 Mcps TDD.>Angle of arrivalRequired>Required precision ofRequiredangle of arrival
In a practical application, contents of the PCAP calculation response message are as depicted in Table 5:
TABLE 5Information element/Optional orgroup namerequiredRangeNoteMessage typeRequiredTransaction identifierRequiredUE location estimationRequired
Along with the development of third generation mobile communications, a Node B tends to be designed by separating a baseband from radio frequencies, and a baseband remote Node B is such a Node B with a baseband separate from a radio frequencies. The Baseband remote Node B is configured with multiple sets of distributed antennas for coverage. A cell portion as defined to be covered by each specific set of antenna can be identified by a cell portion identifier. Thus there may be multiple cell portions of a cell. The RNC determines in which cell portion the mobile terminal is located in the following two approaches:
First Approach:
The mobile terminal has an initial access through the Up Link Frame Protocol (UL FP) of the user plane. The Node B can carry information about a cell portion where the UE is located through the Random Access Channel Frame Protocol (RACH FP) or the Enhanced Uplink Dedicated Channel Frame Protocol (E-DCH FP). FIG. 3 particularly illustrates a format of the RACH FP, wherein for the 1.28 Mcps TDD system, Bit 3 of New IE Flag indicates whether there is a Cell Portion Low Chip Rate (LCR) IE, and particularly 1 indicates that there is a Cell Portion LCR IE, and 0 indicates that there is no Cell Portion LCR IE; and FIG. 4 particularly illustrates a format of the E-DCH FP, wherein for the 1.28 Mcps TDD system, Bit 0 of New IE Flag indicates whether there is a Cell Portion LCR ID IE, and particularly 1 indicates that there is a Cell Portion LCR ID IE, and 0 indicates that there is no Cell Portion LCR ID IE.
Second Approach:
The initially accessing mobile terminal makes a dedicated measurement report through the Node B. After the terminal accesses, the RNC can initiate a Node B dedicated measurement in the measurement type of Best Cell Portions, request the Node B for reporting a Cell Portion of which the UE is located, and support three report modes including a periodical report, an immediate report and a change report, as depicted in Table 6.
TABLE 6Report characteristic typeDedicatedEventEventEventEventEventEventmeasurementImmediatePeriodicalA-modeB-modeC-modeD-modeE-modeF-modeChangetypereportreportreportreportreportreportreportreportreportBestXXXcellportion
It can be seen from above, the RNC can obtain initial location information of the mobile terminal and update location information of the mobile terminal in real time, in the two approaches above. The RNC can position the mobile terminal more precisely, based upon the information about the best cell portion where the mobile terminal is located, but in the latest 3GPP Standard R10, the cell portion information (i.e., the information about the division of the cell into the cell portions) has not been introduced into the PCAP calculation request message of the Iupc interface so far, that is, the PCAP function based upon the cell portion information can not be performed in the existing standard to position the mobile terminal more precisely.